1. Field of the Invention
The present invention relates to catalysts, to methods of making catalysts, to methods of using catalysts, to methods of polymerizing, and to polymers made with such catalysts. In another aspect, the present invention relates to polyolefin catalysts, to methods of making such catalysts, to methods of using such catalysts, to polyolefin polymerization, and to polyolefins. In even another aspect, the present invention relates to Ziegler-Natta catalysts, to methods of making such catalysts, to methods of using such catalysts, to polyolefin polymerization, and to polyolefins.
2. Description of the Related Art
Having been around since the early 1950's, Ziegler-type polyolefin catalysts, their general methods of making, and subsequent use, are well known in the polymerization art.
However, while much is known about Ziegler-type catalysts, there is a constant search for improvements in their polymer yield, catalyst life, catalyst activity, and in their ability to produce polyolefins having certain properties.
U.S. Pat. No. 4,255,544, issued Mar. 10, 1981 to Kimura et al., discloses a process for polymerization of ethylene utilizing a catalyst comprising (A) the reaction product of a magnesium compound and titanium halide, and (B) an organic aluminum compound, wherein component A is prepared by reacting magnesium dialkoxide with a hologen-containing silicon compound and an alcohol to provide a solid material and then reacting the solid material with titanium halide in the presence of an alkoxy-containing silicon compound.
U.S. Pat. No. 4,914,069, issued Apr. 3, 1990 to Job et al., discloses the preparation of an olefin polymerization catalyst component having improved activity and selectivity, which are prepared by (a) halogenating a magnesium compound containing at least one aryloxy, alkyl or carbonate or alkloxy group with a first halide of tetravalent titanium and a first electron donor; (b) contacting the resulting product with a second halide of tetravalent titanium; and (c) washing a resulting treated halogenated product with an inert hydrocarbon liquid. In the process, a second electron donor is used in step (a) or (b), and that the product of step (b) is contacted in a step (b2) with a third halide of tetravalent titanium at a temperature of 40° C. to 140° C. and thereafter the treated product is washed in step (c).
U.S. Pat. No. 5,155,187, issued Oct. 13, 1992 to Shelly, discloses a polymerization method utilizing a catalyst which is the reaction product generally of a silicon-containing compound, a magnesiumdialkyl, an alcohol, a halide-containing metal compound, an aluminum alkoxide, and a second halide-containing metal compound.
U.S. Pat. No.5,610,246, issued Mar. 11, 1997 to Buehler et al., discloses a process for polymerizing propylene using a silica-supported catalyst. The catalyst comprises the product obtained by contacting silica, in random order, with (1) at least one hydrocarbon soluble magnesium-containing compound; and (2) a first modifying compound selected from the group consisting of silicon halides, boron halides, aluminum halides and mixtures thereof followed by a second specified modifying compound.
U.S. Pat. No.5,631,334, issued May 20, 1997 to Zandona, disclose a process for the manufacture of a catalytic solid for the (co)polymerization of at least one olefin, comprising the coprecipitate magnesium and of at least one transition metal.
However, in spite of these advancements in the prior art, none of these prior art references disclose or suggest a heat treatment of a preactivated polyolefin catalyst.
Furthermore, none of these prior art references disclose or suggest that heat treatment of a preactivated polyolefin catalyst will provide any effect on the polymer molecular weight distribution (“MWD”).
Thus, there is a need in the art for a polyolefin catalyst.
There is another need in the art for a method of making a polyolefin catalyst.
There is even another need in the art for a method of polymerizing olefins.
There is still another need in the art for polyolefins of various MWD.
There is yet another need in the art for a polyolefin catalyst allowing for production of polyolefins of various MWD, with a catalyst that also has high activity and excellent fluff morphology.
There is even yet another need in the art for a method of using a heat treated preactivated polyolefin catalyst to effect polyolefin MWD.
These and other needs in the art will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.